1. Field of the Invention
The present invention relates to a mobile node adapted router and a home agent router forming a packet communication system supporting at least mobile nodes among fixed nodes and mobile nodes.
2. Description of the Related Art
As a protocol for mobile nodes enabling communication in an IP network even when nodes change connection points in the network, the Internet Engineering Task Force (IETF) of the U.S. has established the Mobile IP (document [1]: RFC2002) protocol (note: the documents cited in the specification are listed together at the end of the specification).
Due to the rapid rise in the number of nodes serviced by IP networks in recent years, a serious problem has arisen of the depletion of IP addresses. A transition is underway to a network using the IPv6 (document [2]: RFC2460) protocol enabling use of more IP addresses. Therefore, in addition to the Mobile IP protocol in IPv4 networks up to now, effort is being made to establish a Mobile-IPv6 (document [3]) protocol supporting movement of nodes in an IPv6 network. The IETF is engaged in deliberations for the next stage of requests for comments (RFC).
In the Mobile-IPv6 protocol, depending on the configuration of the network or the location of the node, sometimes time is taken for the switching the transfer route when a mobile node (MN) moves. In such a case, there is a problem that if packets are sent from another node to a network connected to before the movement of the mobile node, packet loss occurs and the quality of service deteriorates.
Further, to switch the transfer route, not only the mobile node, but also the correspondent node (CN) communicating with the mobile node has to support the Mobile-IPv6 protocol. Therefore, when the correspondent node does not support the Mobile-IPv6 protocol, the packets to be transmitted to a mobile node are transferred to the mobile node through a home agent router (HA) cooperating with a home link to which the mobile node is normally connected. Therefore, there is a problem of an increase in the transfer delay or concentration of traffic in a home agent router. The above problems will be explained in detail later with reference to the drawings.